A great deal of research has been performed which has relied on the assumption that the Main Intrinsic Polypeptide (MIP) of the ocular lens fiber cell plasma membrane is the protein which comprises the numerous intercellular junctions that exist between these fiber cells. However, the evidence is limited, entirely circumstantial, and, in part, contradictory. Recently, both published and unpublished data has undermined the role of the MIP as a putative junctional protein, and consequent lack of certainty in the composition of the intercellular junctions has slowed related research in the lens. This research proposal aims to define unequivocally which fiber cell plasma membrane protein comprises the fiber cell junctions, thus allowing experimental manipulation of intercellular communication in the lens to proceed, and proceed with confidence. Further, it is now reasonably certain that the hepatocyte gap junction and the lens gap junction, while apparently analogous in function, are not homologous in protein composition. Successful idenfification of the lens gap junction protein will allow for an informative comparision of these two proteins. Completion of this project will help further define normal lens cell function and cellular interdependence mediated by the gap function, thus paving the way for an understanding of lens pathologies related to dysfunction of these processes. In brief the project will be approached by: 1) fractionating fiber cell plasma membrane proteins, 2) immobilizing the fractionated proteins by electrophoretic transfer and covalent linkage to an inert substrate, 3) affinity purifying antibodies to these proteins, 4) screening the antibody subpopulations for junction-binding activity by electron microscope level immunocytochemistry. An crude antiserum with junction-binding ability has already been produced.